It has long been felt that there exists a need for an extremely simple, economical and reliable single-turn potentiometer. One recent development in this search has resulted in the use of a shortened helical spring to form the wiper portion of a rotor assembly. The helical spring replaces earlier wipers of the plural finger type. This recent design included the use of a recess in the rotor for insertion of an element formed of resilient material such as silicone rubber as a backing for the helical spring. The resilient element essentially embraces and presses against the rear portion of the coiled spring wiper which is held in the recess of the rotor. Thus when the rotor rotates, the resilient element helps the wiper slide smoothly along the surface of the resistance element. The individual coil sections of the spring effect multiple electrical contact with the resistance element. In this construction, a rather short coil spring was employed to enhance the smooth sliding of the wiper so as to provide optimum mechanical and electrical characteristics of the potentiometer.
In spite of the improvement in using a coil spring wiper, problems still exist in providing reduced contact resistance variation (CRV) and improved torque control. Problems also exist in providing reliable electrical connections to the substrate element.
The present invention has as an object the employment of a coil-springed wiper in a miniature potentiometer together with other advantages and simplicities of construction.
It is the purpose of the present invention, therefore, to provide a single-turn potentiometer employing a miniaturized coil spring and resilient rubber backing to effect a smooth wiping of a cermet resistance element.
It is another object of the present invention to provide an open-frame unit having a minimum number of parts to enable rapid and economical assembly of the unit.
It is an additional object of the present invention to affix a rotor to a potentiometer including a substrate element wherein the rotor is held by a riveting arrangement.
It is still another object of the present invention to provide a method of affixing a rotor to a substrate in a potentiometer which simultaneously improves the torque and contact resistance variations of the potentiometer.
It is a still further object of the present invention to provide an open frame potentiometer unit wherein the mechanical stop on the unit is obtained by the cooperation of a projection from the rotor together with a portion of the conductor which makes electrical contact with the potentiometer.
A still further object of the present invention is the provision of a novel approach and method for the connection of conductive elements to a substrate.
Still another object of the present invention is the provision of a dust-free closed-frame unit having a built-in stop mechanism and a simplicity of assembly and construction.
It is still an additional object to provide a potentiometer having optional resistance material on its substrate which may be inserted in series with the terminals of the potentiometer by laser removal of resistance material.
Other objects of the present invention will become apparent by reference to the following description and drawings while the scope of the invention will be pointed out in the appended claims.